Numerals or figures are the glyphs in a typeface that represent numbers. In many fonts, it’s possible to select different kinds of numerals intended for different uses.
Numerals can either be “lining” (uppercase-like), or “oldstyle” (lowercase-like), or “proportional” (with varying character width), or “tabular” (with a unified character width, a la monospaced type). Therefore, there are effectively four flavors of numeral. Explore them at length in our article, “Understanding numerals”.